My favorite theory Columbo theory (which does check out up until the later seasons) is that there is no mrs Columbo, it's part of the dumb schlub act he puts on to trap the suspects.
The Season 3 or 4 finale the Police chief is trying to frame a suspect for the murders he's committed and Columbo traps him by switching his own address with the framed suspect and lets the Chief plant false evidence. In the process we see Columbo lives in a really dingy run-down apartment, with no signs of a wife. It's one of the very rare glimpses into his real private life, since most often he's not shown at home but in a diner or a pool-hall when not working.
The Mrs. Columbo spinoff was so poorly received that they had her divorce him off-screen to justify changing her last name. When when that pissed off fans (and Peter Falk) even more, they retconned her connection to Columbo entirely, with her ex-husband now suddenly being some other guy named Philip.
After the Mrs. show was cancelled, Columbo went back to talking about his wife.
Conclusion: Columbo never actually had a wife. And "Mrs. Columbo" was a holodeck program used by a young Katherine Janeway, and at some point she rewrote her character's backstory when she decided she didn't want it to be fanfiction anymore.